Heretofore, metering rods have been suspended by a metallic hanger and in the event the metering rod was maintained in contact with a side of the orifice formed by the metering jet, a separate spring element has been mounted on the hanger support to urge the metering rod into engagement with the side forming the orifice such as shown in U.S. Pat. No. 2,099,106 issued Nov. 16, 1937. When the metering rod is in contact with one side of the orifice, the flow will remain substantially the same for a given suction and the flow rate may be calibrated accurately. If the metering rod could be accurately held in the center of the orifice without interfering with the longitudinal movement of the metering rod the carburetor would function properly but no practical and convenient means of doing this is available particularly in view of manufacturing tolerances resulting from mass production. Thus, it is desirable to have the metering rod continuously held in engagement with the side forming the orifice in which the lower end of the metering rod is positioned.
Additionally, heretofore, an adjusting screw for adjusting the height of the metering rod during the flow testing has been provided and in order to maintain such setting accurately, a spring has been positioned between the hanger support for the metering rod and the head on the adjusting screw.